Hop is used as raw material for the production of beer. Hop provides the bitter impression of beer but also an elongated shelf life due to its antibacterial effect.
The most important compounds contained in hop are, besides the bitter acids (e.g. α-acids), essential oils, tannins and polyphenols.
Xanthohumol, a prenylflavonoid (polyphenol) of hop which occurs in the lupulin glands of the hop cones has a plurality of positive effects. Beside the antiviral and the anti-oestrogenic and anti-inflammatory effect, a cancer-chemo preventive activity of XN is also discussed which activity is currently under investigation in animal experiments. The content of xanthohumol in hops varies depending on the hop variety between 0.1 and 1%. The hop varieties having a high content of xanthohumol usually comprise a high portion of bitter substances.
Hop products may be divided in raw hops, hop pellets and hop extracts. Since xanthohumol occurs only in the lupulin glands of the hop cone, hop pellets exhibit a high content of XN corresponding to the accumulation of α-acids. Hop extracts may be obtained by extraction with CO2 and/or ethanol. Whereas CO2 extract hardly comprises any xanthohumol XN is extracted almost completely during the ethanol extraction. Recently, XN enriched products are produced by a combination of both extraction methods. Depending on the production method XN contents of between 8 and 99% are achieved. The production of hop extracts enriched with XN and drinks comprising XN is described e.g. in the patents DE 19939350, DE 10256031, DE 10240065 and EP 1431385.
In the brewing process xanthohumol is relatively instable and is mainly precipitated via the trub, the yeast, by filtration and stabilisation due to its limited solubility. Besides, xanthohumol is isomerised to iso-xanthohumol which also has a positive effect, however, to quite a lower extent compared to xanthohumol. With the conventional method less then 0.2 mg/l XN are reached in the final beer in most of the cases. In some stout or porter type dark beers XN contents of up to 1.2 mg/l XN were found (Walker et al., Brauwelt 2003). With a special brewing method which applies late hopping and a fast cooling of the beer wort it is possible to increase the XN content in non-filtered pale beers to 1-10 mg/l (DE 102 56 166).
It is an advantage of the present invention that the isomerisation of xanthohumol to iso-xanthohumol is suppressed to a large extent due to the improvement of the brewing method. Therefore, it is possible to increase dosage amounts of XN without allowing the beers to become unpleasantly bitter, for instance. Further, the addition of stabilisers is possible which would normally lead to a relevant decrease in the XN content.
A method for producing the roasted extract comprising XN from roasted products of cereals, cereal malt, coffee or cacao and a hop extract comprising XN is an object of the present invention. The hop extract comprising XN is characterised by a particularly high content of xanthohumol. It is in the range from 10 mg to 2 g/kg, preferably in the range of 200 mg to 850 mg/kg. Due to the use of this roasted extract beers with a significant increased content of XN compared to the prior art can be obtained in accordance with the German purity law, for instance.
Herein, “roasted extract comprising XN” denotes an extract which is obtainable from a roasted extract from roasted products of cereals, cereal malt, coffee or cacao and from the hop extract comprising XN. “Roasted extract” denotes a cold or hot extract from coarsely ground or non-ground roasted malt or cereals and includes a hot or cold extract from coffee or cacao; “cereal malt” denotes a cereal that was artificially or controllably allowed to germinate, and “hop extract comprising XN” denotes an extract from hops which was obtained with the aid of a solvent and exhibits an increased content of XN. “Basic materials” is a collective term for plain or combined substances which may be of natural or synthetic origin. They are used as parent material for the further production of food products. In the present invention basic materials denote e.g. essences which may be enriched with XN as well as e.g. a basic material for coke according to an embodiment of the present invention.
For producing roasted extract comprising XN a hot aqueous extract of the ground roasted products e.g. of barley, wheat, rye as well as the corresponding malts, coffee beans or cacao beans is prepared. A hop extract comprising XN is added thereto at the beginning of the heating period. The extraction of xanthohumol in the extractions of the roasted products leads to a XN content which is by far higher than the solubility limit of XN in typical aqueous solutions. This amounts to 1.3 mg/l of XN at a water temperature of 23° C. and to 1.1 mg/l of XN at a water temperature of 8° C.
Soluble roasted substances which adsorb or bind XN and therefore, apparently keep it in solution, are probably responsible for the high yields of xanthohumol in the extracts. The extracts may be fermented, concentrated or clarified without noteworthy losses of XN. According to one embodiment of the present invention a xanthohumol content of approximately 1320 mg/kg was obtained in the extract after concentration of the XN comprising roasted malt wort.
The XN comprising roasted malt wort may be used in the food industry such as in the brewing and beverage industry as well as in the foodstuff industry. Thus, the application of the XN comprising roasted malt wort may lead to an enrichment of xanthohumol in spirits, herbal spirits, herbal liquor wine, beer, mixed drinks comprising beer, or bitters, and also of non-alcoholic drinks or drinks with reduced alcohol content such as malt beverages, coffee, coffee substitute, cacao, ice tea or soft drinks as well as of basic materials for the production of such products in a simple, safe and economic way. A particular advantage is that a roasted malt beer enriched with XN and prepared according to this method may be added to a conventionally produced beer at any time of the beer production in accordance with the purity law, i.e., without the use of emulsifying agents or other chemical additives.
An enrichment of food products with xanthohumol, such as bakery products, backing kits, parfaits, dairy products (e.g. yoghurt, curd cheese and mixed drinks comprising milk) desserts, ice cream, meat products, sauces and herbal candies as well as enrichment of pharmaceutical products with xanthohumol, such as cough syrup, is also possible.
The method for preparing an aqueous extract comprising XN from roasted products of cereals, cereal malt, coffee or cacao comprises the following process steps:                a) addition of a hop product comprising XN to an extract which is mainly or completely produced from roasted or colour malts, respectively, or roasted barley; wherein the added hop product has a content of XN which is, related to the mass used for its production, at least 5 times that of the hops used for its production; and wherein after the addition of the hop product comprising xanthohumol to the aqueous roasted extract the dissolving or even an intensive dissolving of XN is reached, despite the original low solubility in aqueous solutions;        b) dissolving of XN by pre-dissolving of the XN comprising hop product in ethanol;        c) dissolving of XN by agitating, mixing, shaking, supersonic treatment, ultraturax treatment or other mechanical forces;        d) dissolving of XN by heating of the roasted extract;        e) dissolving of XN by application of an alternating current;        f) wherein the amount of the addition of the hop product comprising XN is at least 50 mg XN per liter.        
As will be understood from the following examples, it is not necessary that all of the previously mentioned process steps are realised when implementing the process. The process steps b) to h) are optional.
In the following, examples of methods according to the present invention and beverages produced thereby are given.